Recently, Bluetooth, wireless personal area network (WPAN) technology has been developed, which allows audio or video data to be exchanged between devices by configuring a wireless network between a relatively small number of digital devices in limited places such as homes or small-scaled companies. WPAN can be used to exchange information between a relatively small number of digital devices in a relatively close distance, and enables communication of low power and low cost between digital devices.
FIG. 1 illustrates a configuration example of WPAN. As shown in FIG. 1, the WPAN is a network configured between devices within a limited place such as home. The network is configured by direct communication between devices to enable seamless exchange of information between applications. Referring to FIG. 1, the WPAN is comprised of at least two user devices 11 to 15, wherein one of the user devices is operated as a coordinator 11. The coordinator 11 serves to provide basic timing of the WPAN and control quality of service (QoS) requirements. Examples of the user devices include computer, PDA, notebook computer, digital TV, camcorder, digital camera, printer, mike, speaker, headset, barcode reader, display, and cellular phones. All digital devices can be used as the user devices.
The WPAN is an ad hoc network (hereinafter, referred to as ‘piconet’) which is not previously designed but formed if necessary without assistance of a central infra. The procedure of forming one piconet will be described as follows. The piconet starts in such a manner that a random device that can be operated as a coordinator performs a function of a coordinator. All devices start a new piconet or perform scanning before association with the existing piconet. Scanning means that a device collects and stores information of channels and searches the presence of the existing piconet. A device which has been instructed from an upper layer to start a piconet forms a new piconet without association with a piconet which is previously formed on a random channel. The device starts a piconet by selecting a channel having little interference based on the data acquired during scanning and broadcasting a beacon through the selected channel. In this case, the beacon is timing allocation information, information of other devices within the piconet, and control information broadcasted by a coordinator to control and manage the piconet.
Since the state of the channel used in the wireless network is variable temporally, even though desirable communication between devices can be performed owing to good state of the channel when the wireless network is formed, a problem in performing communication between devices may occur as the channel state becomes poor in accordance with the lapse of the time. Accordingly, it is necessary to continuously assess and search a state of a channel which is being currently used in the wireless network and states of other channels in addition to the current channel. As a result, if there is another channel that can be used by the wireless network and has a better state than that of the current channel, the current channel can be changed to the better channel to continue to enable desirable communication.